netdev - Re: [PATCH 4/6] seccomp: add a way to access filters via bpf fds

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Date:	Fri, 4 Sep 2015 13:29:49 -0700
From:	Alexei Starovoitov <alexei.starovoitov@...il.com>
To:	Kees Cook <keescook@...omium.org>
Cc:	Tycho Andersen <tycho.andersen@...onical.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Will Drewry <wad@...omium.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	Pavel Emelyanov <xemul@...allels.com>,
	"Serge E. Hallyn" <serge.hallyn@...ntu.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	LKML <linux-kernel@...r.kernel.org>,
	Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH 4/6] seccomp: add a way to access filters via bpf fds

On Fri, Sep 04, 2015 at 01:26:42PM -0700, Kees Cook wrote:
> On Fri, Sep 4, 2015 at 9:04 AM, Tycho Andersen
> <tycho.andersen@...onical.com> wrote:
> > This patch adds a way for a process that is "real root" to access the
> > seccomp filters of another process. The process first does a
> > PTRACE_SECCOMP_GET_FILTER_FD to get an fd with that process' seccomp filter
> > attached, and then iterates on this with PTRACE_SECCOMP_NEXT_FILTER using
> > bpf(BPF_PROG_DUMP) to dump the actual program at each step.
> 
> Why is this a new ptrace interface instead of a new seccomp interface?
> I would expect this to only be valid for "current", otherwise we could
> run into races as the ptracee adds filters. i.e. it is not safe to
> examine seccomp filters from tasks other than current.

same question.
I thought we discussed to add a command to seccomp() syscall for that?

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